This invention relates to the field of sound generating devices. More specifically, it relates to sound synthesizing circuits capable of reproducing common sound, such as, words, noise, music and the like. Such circuits find application where it is desired to permit devices to communicate or interact with human beings for various purposes. For example, it is becoming desirable to permit computers to interact with human beings by methods other than printers or CRT displays. For that purpose it would be desirable to have a synthesizing circuit which could permit a computer to "talk" to a user.
Other applications include educational uses, uses to provide alarm and warnings in the event that malfunctions are detected and finally such circuits find application when used for a wide variety of consumer products including those which may be broadly categorized as games. Such circuits find wide use in the game category in arcade games, home video games, pinball games, and the like. In these applications the sound circuit may be used to provide an incentive to play the games or as a reward for achieving certain goals set up in the game as, for example, obtaining a high score, winning a free game or activating a sequence of targets in a desired order. The addition of sound to such games enhances their attractiveness to the players and makes the experience more enjoyable.
One approach in producing synthesized sound is to store the entire waveform corresponding to the desired sound in a read only memory (ROM) in digitized form. A clock circuit in conjunction with necessary logic is then used to sequentially clock out the waveform to an audio circuit. Such an approach is limited in that number of sounds which can be produced is a function of memory space available which space is expensive.
An alternate method of generating synthesized sounds includes the use of a circuit having a plurality of oscillators and means for gating the oscillators on and off for producing various noise sounds. Again, the resulting output which can be produced by such a circuit is clearly limited.
It is accordingly an object of the present invention to provide a digital sound synthesizing circuit which is more flexible and has greater capabilities than those previously developed.
It is another object of the invention to provide a processor controlled sound synthesizing circuit which can alter one or two basic waveforms stored in a memory in myriad ways to produce different sounds, as desired, responsive to a switch input to the processor.
It is another object of the invention to provide a processor controlled sound synthesizing circuit capable of producing a large family of sounds with only a small memory associated therewith by utilizing program control to digitally alter the waveforms.
A further object of the invention is to provide a sound synthesizer for an arcade type game in which sounds are produced according to the received inputs from said game.
Other objects and advantages of the invention will be apparent from the remaining portion of the specification.